1. Technical Field
The technical field relates to a lens barrel with which the focal distance can be changed.
2. Description of the Related Art
Digital single lens cameras with which an optical image of a subject can be converted into an electrical image signal and outputted have rapidly grown in popularity in recent years. These digital single lens cameras generally have an interchangeable lens configuration, with which lenses can be attached and removed.
With this type of interchangeable lens unit, a stepping motor equipped with an encoder is sometimes employed as the actuator that drives the lens group (see, for example, Japanese Laid-Open Patent Application H08-266093). With this actuator, the direction of rotation of the stepping motor, its speed, angle information, and electrical phase angle information can be accurately detected on the basis of the output from the encoder. When drive is controlled on the basis of the electrical phase angle, this raises the resolution of the rotational angle position, and also greatly increases the rotational speed.
A lens mount that is mounted to a camera body is provided to the interchangeable lens unit. A lens mount contact and an electrical substrate are provided around the lens mount. The lens mount contact is electrically connected to a body mount contact of the camera body. The electrical substrate is connected to the lens mount contact. Electronic parts are mounted on the electrical substrate. Information can be sent back and forth between the interchangeable lens unit and the camera body via the lens mount contact and the body mount contact.
Thus, contacts, the electrical substrate, and electronic parts are packed closely together around the lens mount.
However, if the above-mentioned actuator is disposed around the lens mount, there is the danger that noise generated from the contacts, the electrical substrate, etc., will affect the encoder detection result. Japanese Laid-Open Patent Application 2004-77925 discloses a configuration around a lens mount, but discloses nothing at all about the layout of the actuator that would take the effect of noise into account.